Question

I need help
What are the foci of the following graph?

http://i729.photobucket.com/albums/ww292/akatushi101/focidoe.gif


(0, -5) and (0, 5)

(-5, 0) and (5, 0)

(-4, 0) and (4, 0)

(0, -4) and (0, 4)

Answer 1

a=5, b=3
a^2-b^2=c^2
25-9=16=c^2
c=4
Focal points: (4,0) and (-4,0)

Answer 2

from the picture we see that it is
\[\frac{^2}{5^2}+\frac{y^2}{3^2}=1\] the 5 and the 3 from the endpoints of the ellipse.
the length of the foci is given by pythagoras as
\\sqrt{a^2-b^2}=\sqrt{5^2-3^2}=\sqrt{16}=4\]

Answer 3

\[\sqrt{a^2-b^2}=\sqrt{5^2-3^2}=\sqrt{16}=4\]